102(3)_str45

 

ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 102, No. 3 (2015), p. 351–358
DOI 10.13080/z-a.2015.102.045

The effect of wheat bread contamination by the Bacillus genus bacteria on the quality and safety of bread

Lina VAIČIULYTĖ-FUNK, Renata ŽVIRDAUSKIENĖ, Joana ŠALOMSKIENĖ, Antanas ŠARKINAS

Abstract

The aim of the study was to determine the level of contamination of white bread by aerobic spore-forming bacteria that may cause the ropiness and to evaluate the antimicrobial activity of lactic acid bacteria against aerobic spore-forming bacteria during the storage of wheat bread at different temperatures. The contamination of dough samples by aerobic spore-forming bacteria did not affect the quality of bread in the initial storage phase (6–16 h after baking). The critical Bacillus subtilis subsp. spizizenii ATCC 6633 levels that cause ropiness in baked bread were determined: 7.8 × 106 CFU (colony forming units) g-1 after storage of samples for 3 days at 2 ± 2°C, 1.3 × 106 CFU g-1 after storage of samples for 3 days at 18 ± 2°C and 6.0 × 106 CFU g-1 after storage of samples for 1 day at 30 ± 2°C temperature. It was determined that contamination of dough by aerobic spore-forming bacteria should not exceed 1.0 × 103 CFU g-1. The evaluation of antimicrobial activities of lactic acid bacteria from Lactococcus and Lactobacillus genera against aerobic spore-forming bacteria was performed using an agar well diffusion method. In wheat bread, that had been fermented with Lactobacillus delbrueckii subsp. bulgaricus 148/3, L. acidophilus 336 and L. casei subsp. casei, the antimicrobial effects were observed for up to 3 days of storage at 18 and 30°C temperature. Weak signs of ropiness spoilage (sweet rope odour, discoloration of the crumb) were observed during the storage of the bread samples at 18 ± 2°C for 5 days (1.7 × 102 CFU g-1) and at 30 ± 2°C for 3 and 5 days (1.5 × 102 CFU g-1).

Key words: Bacillus subtilis, lactic acid bacteria, ropiness, wheat bread.

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